1. Field of the Invention
The present invention relates to an image scanner (briefly called a scanner), and especially to the scanner with an automatic document feeder (ADF) and single-side/double-side document scanning modes.
2. Description of the Related Art
A prior art flat-bed scanner 1 with ADF is shown in FIG. 1. The scanner 1 contains an optional automatic document feeder (ADF) 11 and a scanner body 12. The ADF 11 can feed a plurality of document sheets in a document input tray one by one into the scanner body 12. In addition, there exist two fixing posts 14 and an electric connector 15 in the ADF 11. The fixing posts 14 are plugged into the related plug-in holes 16 to mechanically secure the ADF 11 on the flat bed of the scanner 1, and the electric connector 15 is connected to the other electric connector 17 to communicate with scanner 1.
FIG. 2 is a side view of the ADF 11 described above. The stacked plurality of document sheets (not shown in FIG. 1) are put into the document input tray 13 in order. With the cooperation of the document separating roller 111 and the pressing plate 112, the first document sheet on the top is separated from the other document sheets and then is fed into the document sliding channel 115 for scanning, and then this document sheet is transported forward into the document output tray 18 by a couple of document enter rollers 113 and a couple of document exit rollers 114. Under the bottom of the document sliding channel 115 in the ADF 11, there is a scanning slit which serves as the document scanning window, as shown in FIG. 2. In order to let a document sheet smoothly pass through the document scanning window and successfully enter the rear section of the document sliding channel 115, there is a transparent thin film guide 116 under the document scanning window in the bottom of the scanner body 12 to connect the front and rear sections of the document sliding channel 115.
FIG. 3 is an exploded perspective view of a double-side scanner 2 of the prior art. The double-side scanner 2 contains an automatic document feeder (ADF), a upper side digital image capture device 22 and a underside digital image capture device 23, while the ADF contains a plurality of document feeding rollers 24, 25, 26, and 27, a document input tray 28 and a document output tray 29. The stacked plurality of document sheets are put in the document input tray 28. With the document separating mechanism, the first document sheet is separated from the other document sheets. Then, the document sheet is transported through the document sliding channel between the upside digital image capture device 22 and the underside digital image capture device 23 by using the document feeding rollers 24, 25, 26, and 27. Consequently, the double sides of the document sheet are scanned. Finally, the document sheet is delivered into the document output tray 29.